Process for dyeing animal fibers fast tints



Patented Apr. 18,1933

PATENT omen rnrrz s'rnnuli, or BasEL, swxrznnnazm, Am)" nnnma'nn SCHNEIDER, or RIE'HEN NEAR BASEL, SWITZERLAND, hssronons or BASEL, SWITZERLAND- r rnoonssroa nYEI m ammnLrIBnns FAST TINTS TO SOCIETY OF CHEMICAL INDUSTRY IN BASLE,

No Drawing. Application filed September 15, 193i), SeriaINo. 482,155, and in Switzerland September The present invention relates to a process for dyeingani'mal fibers fast-tints. It-comprises the new dyeing process, as well as-the material dyed according to the'newsprocess.

It is known that :theohromium compounds or other metal compounds of azo-dyestufi's containing. groups capable ,of being metallized have acquired considerable importance in the wool dyeing industry'in that they permit the production of well equalized tints of remarkable fastness on wool or other animal fiber by merely dyeing in asulfuric acid bath. However, dyeingin a sulfuric acid bath does not attain the desired object in the case of the chromium compounds of azo d'y t fi of the general formula r s v VJ Y II= N R wherein R stands for a naphthol. 'These dyestuffs are precipitated in "the sulfuric acid bath before they are absorbed by the fiber so that there are obtained weak, ,dyeings, which are not fast. {If it is attemptedto dye the material with these dyestuffs in an organi'cacid, bath, the dyestufl' canbe completelfy absorbed on the fiber but the correct depth 0 dyeing or the valuable properties of fastness or both are not attained. 5 e v v The present invention is based-on the surprising observation that it is possible to dye animal fiberswiththedyestuffs of the above mentioned general formula fast tints by first dyeing the fiber in a weakly acid bath and then converting the dyestufi absorbed by the fiber into new complexes by developing it in Y the same dye-bath by heating or boiling, which bath is made stronger acid by the addition of an acid. At the initial dy'e in weakly acid bath, in w ich the dyestufi' is absorbed by the fiber completely or partially, the addition of organic acids, as for example formic acid, acetic acid, oxalic acid, is expedient, but there may also be used inorganic acids if these latter are added slowly and operation from a in small quantities to the dyeing bath.

chloric acid, are particularly suitable, but.

the use of organic acids, if these are added in" larger quantities, also leads to good results. Q

Theessential moment for the success of the present dyeing process resides in the fact that in the developing bath the dissociation of the added acid must be farther advanced than in,

the initial dyeing bath, i. e. the pH of the developing bath must be smaller than the pH-of the dyeing bath.- It is lmown that inthe case of non-metalliferous dyestuffs capable of dyeing in presence of organic acids the ab-.

'sorption of the dyestuffs-can be completed by the addition of a mineralacid at the end of i the dyeing process. The process in accordance with the present invention, however,dif-

fers from the aforesaid procedure in that it.

comprises the further development of dye stufis which are/present on the fibre or, respectively, their conversion into other complexes.

The following examples illustrate the in vention, the parts beingby Weight:

Example 1 Theldye-bath'is prepared from '2000 pa rt s V of Water, 56 parts of formic acid, which may if desired be addedin portions during dyeing, and 3-4 parts'of the chromiumcompound ofthe ,dyestufl of the formula obtainable as described copending specification Serial No. 482,364

in Example 1 of the filed September 16, 1930. parts of wool are entered into the bath at 90 C. Dyeing islcontinued for a quarter of an'hour and the temperature is then raised'to boiling in the course of a further-. hour. This temperature is maintained for some time until the dyestuff is absorbed, whereupon 67 parts of concentrated sulfuric acid are added and the bath is boiled until the dyestuff is completely developed, this operation requiring about to 1 hour. The wool is thereby dyed a deep black tint of very good fastness properties.

It is also possible to conduct the dyeing using from the start sulfuric acid alone, if care be taken that before the dyestufi' is absorbed the pH value of the dye-bath is not substantially less than that of the dye-bath containing the formic acid; this may be obtained by adding mineral acid to the bath very slowly and gradually or by adding a formate to the bath at the commencement.

Example 2 The printing color is prepared by dissolving 20 parts of the chromium compound obtainable as described in Example 1 of the copending specification Serial No. 82,36& filed September 16, 1930 and 60 parts of neutral starch tragacanth thickening in 380 parts of water. The material is printed with this printing color in the usual manner. After drying it is steamed for 1 hour in a Mather- Platt apparatus at an over-pressure of A; atmosphere, then it is rinsed with water and finished in the usual manner. There are thus obtained on wool or silk black prints of very good fastness properties.

What we claim is 1. Process for dyeing animal fibers fast tints, consisting in first dyeing the fiber in a weakly acid bath with the chromium compounds of azo-dyestuifs of the general formula NO2 I SOaH wherein R stands for naphthol, and then converting the dyestuif absorbed by the fiber into new complexes by developing it in the same bath which is made stronger acid by the addition of an acid.

2. Process for dyeing animal fibers fast tints, consisting in first dyeing the fiber in a weakly acid bath with the chromium compound of the azo-dyestuff of the formula OH HO $0311 and then converting the dyestufi absorbed by the fiber into new complexes by developing it in the same bath which is made stronger acid by the addition of an acid.

3. Process for dyeing animal fibers fast tints, consisting in first dyeing the fiber in an organic acid bath with the chromium compound of the azo-dyestuif of the formula ITT' =N and then converting the dyestufi' absorbed by the fiber into new complexes by developing it in a bath which is made stronger acid by the addition of an acid.

4- Process for dyeing animal fibers fast tints, consisting in first dyeing the fiber in an organic acid bath with the chromium compound of the azo-dyestuff of the formula LIZ-2:21? A OH HO NOgand then converting the dyestufi' absorbed by the fiber into new complexes by developing it in the same bath which is made stronger acid by the addition of an inorganic acid.

6. Process for dyeing animal fibers fast tints, consisting in first dyeing the fiber in a bath containing formic acid with the chromium compound of the azo-dyestufi' of the formula and then converting the dyestuif absorbed by the fiber into new complexes by developing it in the same bath which is made stronger acid by the addition of sulfuric acid.

In order whereof we have hereunto signed our names this 6th day of September 1980.

FRITZ STRAUB. HERMANN SCHNEIDER. 

